<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        //如果表达式一为真  返回表达式二
        console.log(123&&456) ;  //456

        if(123&&'鲁大师'){
            alert("11111111")
        }

        if(123&&0){
            alert("222222222")
        }

        console.log(123&&456&&789);   //789

        console.log(0&&456);   //0
        console.log(123&&0&&789);  //0

        var num=10
        console.log(123&&num++);   //10
        console.log(123&&++num);     //12




    </script>
</head>
<body>

</body>
</html>